Surgery on the eye is becoming more commonplace and sophisticated as new techniques and devices are developed to combat impaired sight or even blindness. One such field of surgery is the replacement of the lens in the eye which can be necessitated, for example, by cataract development, which opacifies the lens.
Procedures have been developed for removal of the lens. Early procedures have involved the removal of the lens and lens capsule (transparent membrane encapsulating the lens) by means of forceps or suction. More recently, less traumatic means have been developed; such means involve particulating the lens, an example of which is called sonication, which involves ultrasonic disintegration of the lens by application of high frequency vibrations thereto. The lens fragments are then removed by aspiration.
Replacement of the lens to avoid requiring the patient to wear spectacles with massive lenses has been investigated. Some solutions have included injecting a viscous liquid or a silicone into the vacant lens capsule. Implantation of intraocular lenses has also been done, but the implant is rigid and not focusable and is easily dislodged by shock or vibration.
More recently, G. M. Wright and T. D. Talcott in U.S. Pats. 4,537,943; 4,542,542; and 4,608,050 have disclosed injection by needle of a polymer composition into the lens capsule. The polymeric composition comprises a silicone prepolymer, a cross-linker and a platinum-based catalyst. The composition cures in the lens capsule to an optically clear, gel-like material which may accommodate, or focus, through action of the eye lens muscle.
However, a problem with the polymeric composition disclosed by the prior art is that a separate heating step is required to permit removal of the needle from the eye to initiate polymerization at the injection site and thus prevent loss of polymer therefrom. Further, the time of initial cross-linking is on the order of several hours, which involves lengthy immobilization of the eye to permit complete curing.
Thus, what is required is a polymeric composition providing the advantages of the prior art while avoiding most, if not all, the problems associated with the prior art approaches.